Xenarc 700TSV Offset at 800x480?

I am running Windows XP on a Via SP13000 connected to a Xenarc 700TSV with the Streetdeck front end. It has been running pretty good for six months at an 800 x 600 resolution. Today when I started the car the Via BIOS graphic displayed normally, the screen auto sync'd to 1024x768 and displayed the restarting Windows graphic normally. Then the screen auto sync'd to 800x600 and when it displayed the Windows desktop (and subsequently displayed the Streetdeck interface) the image was offset to the right by approximately 200 pixels. In other words there was a 200 pixel wide black stripe on the left-hand side of the monitor and then the expected image started at pixel 201 and continued off the right-hand side of the screen (the 200 pixel number is an approximation.)

The touchscreen continues to function as normal in that I need to touch the screen where the button *should* be in order to activate the button even though the button graphic is displayed 200 pixels to the right.

I changed the Windows resolution to 1024x768 and everything lines up fine. I returned to 800x600 and the 200 pixel offset returned. Rebooting didn't help. The cabling all appears to be undisturbed and solid.